C1-inhibitor deficiencies (hereditary angioedema): where are we with therapies?

Hereditary angioedema, an autosomal dominant disorder, presents clinically as recurrent episodes of swelling. It results from either deficient production or function of C1 inhibitor. Acquired angioedema is associated with lymphoproliferative or autoimmune disease. Conventionally attenuated androgens and antifibrinolytics have been used for prophylaxis, both for the long term and presurgically. Fresh frozen plasma and plasma-derived C1 inhibitor concentrate have been used primarily for treatment of acute attacks. All have drawbacks in side effects or potential for infection transmission. New treatments (recombinant C1 inhibitor, icatibant, DX-88, and for acquired angioedema, rituximab) so far show good safety profiles. Early data suggest these may be effective treatment alternatives. The efficacy of current treatment and the potential held by newer agents that target specific elements in complement or kinin pathways are examined. Some agents are likely to have a wider role in treatment of other, more common, forms of angioedema.

Laboratory testing for C1 inhibitor deficiency: a comparison of two approaches to C1 inhibitor function.

BACKGROUND: C1 inhibitor deficiency may be hereditary or acquired. It is characterized by absent or poorly functioning C1 inhibitor. The disorder is rare, with prevalence estimated at 1/50,000. The very low incidence of the condition makes the sensitivity and specificity of assays used particularly important. Two different methods are commercially available to measure C1 inhibitor function. There are few data comparing these assays. METHODS: Two assays of C1 inhibitor function (C1 inhibitor-C1s complex formation or inhibition of C1 esterase cleavage of artificial substrate [colorimetric]) were compared in 71 patients (28 hereditary angioedema, 2 acquired angioedema and 41 controls). RESULTS: Qualitatively, the two assays showed good correspondence (92%). Six of 71 results were discordant. Correlation in quantitative terms was moderate (R = 0.81). CONCLUSIONS: Both assays show high sensitivity for hereditary/acquired angioedema. The colorimetric assay is more prone to false-positive results. However, clinical interpretation is not adversely affected.

C1 inhibitor deficiency: management.

This is the second of two articles on C1 inhibitor deficiency based on a recent UK consensus document covering its diagnosis and management in adults and children. This summary focuses on the management of the disorder including prophylaxis, emergency treatment and special situations such as pregnancy and dental care.

C1 inhibitor deficiency: diagnosis.

This is the first of two articles on C1 inhibitor deficiency based on a recent UK consensus document covering diagnosis and management of the disorder in both adults and children. This paper focuses on diagnosis of this disorder.

C1 inhibitor deficiency: consensus document.

We present a consensus document on the diagnosis and management of C1 inhibitor deficiency, a syndrome characterized clinically by recurrent episodes of angio-oedema. In hereditary angio-oedema, a rare autosomal dominant condition, C1 inhibitor function is reduced due to impaired transcription or production of non-functional protein. The diagnosis is confirmed by the presence of a low serum C4 and absent or greatly reduced C1 inhibitor level or function. The condition can cause fatal laryngeal oedema and features indistinguishable from gastrointestinal tract obstruction. Attacks can be precipitated by trauma, infection and other stimulants. Treatment is graded according to response and the clinical site of swelling. Acute treatment for severe attack is by infusion of C1 inhibitor concentrate and for minor attack attenuated androgens and/or tranexamic acid. Prophylactic treatment is by attenuated androgens and/or tranexamic acid. There are a number of new products in trial, including genetically engineered C1 esterase inhibitor, kallikrein inhibitor and bradykinin B2 receptor antagonist. Individual sections provide special advice with respect to diagnosis, management (prophylaxis and emergency care), special situations (childhood, pregnancy, contraception, travel and dental care) and service specification.

Subclinical hypothyroidism: a comparison of strategies to achieve adherence to treatment guidelines.

BACKGROUND: Subclinical hypothyroidism is an entity based on the laboratory findings of a raised serum thyrotrophin (TSH) concentration and a normal free thyroxine (FT(4)) concentration. Patients with subclinical hypothyroidism who also have anti-thyroid peroxidase (TPO) antibodies have a higher conversion to overt hypothyroidism than those without, and treatment with thyroxine is recommended. METHOD: We audited anti-TPO assay requests within two NHS Trust hospitals, against consensus standards, to ascertain whether a cascade approach to anti-TPO testing and direct advice leads to more appropriate prescribing of thyroxine in general practice. RESULTS: Our data show that where anti-TPO status was automatically tested for and clear advice for treatment given, >85% of patients were treated according to the standard required by the consensus document, with >90% of those recommended to be commenced on thyroxine actually doing so. In contrast, where anti-TPO was not routinely assessed, treatment was started in 46% of patients, without clear evidence that this was appropriate. CONCLUSION: In order to better advise clinicians and in accordance with the agreed protocol, laboratory-generated cascade testing for anti-TPO antibodies should be an integral part of the investigation of subclinical hypothyroidism, and reports should contain appropriate interpretation and advice.

Echocardiographic abnormalities in primary antibody deficiency.

OBJECTIVE: To document cardiac abnormalities secondary to pulmonary disease in primary antibody deficiency. PATIENTS AND METHODS: A cross sectional audit study of patients from a regional immunology centre. Subjects undergoing two dimensional and Doppler transthoracic echocardiography were reviewed. Ventricular dimensions and function, valvular competence, and estimated pulmonary artery pressure were recorded. Data were compared with clinical variables, pulmonary function tests, and thoracic computed tomography data. RESULTS: Nineteen patients with common variable immunodeficiency and one with IgG(2) subclass deficiency were included, mean age at diagnosis 37.5 years, mean estimated diagnostic delay 10.94 years. Left ventricular impairment was found in 15% and right heart dilatation in 20%. Pulmonary hypertension (mean pulmonary artery pressure >25 mm Hg) was found in 45% (9/20), graded as moderate (40-60 mm Hg) in 44% of cases. Pulmonary function was obstructive in 47% (9/19). Fifty five percent of the patients with computed tomography data within the last five years (10/18) had confirmed bronchiectasis. Patients with right heart dilatation and/or moderate pulmonary hypertension (n = 6) had a more prolonged diagnostic delay (p = 0.04) and more severe lung disease. CONCLUSION: Echocardiographic abnormalities are common in primary antibody deficiency, associated with diagnostic delay and pulmonary complications. Pulmonary hypertension should be considered in those with severe lung disease and can be confirmed by echocardiography.

Lymphoproliferative disease in antibody deficiency: a multi-centre study.

We have undertaken a retrospective study of antibody deficient patients, with and without lymphoma, and assessed the ability of specific polymerase chain reaction (PCR) primers to determine if the detection of clonal lymphocyte populations correlates with clinical and immunohistochemical diagnosis of lymphoma. We identified 158 cases with antibody deficiency presenting during the past 20 years. Paraffin-embedded biopsy specimens or slides were available for analysis in a cohort of 34 patients. Of these patients, 29 had common variable immunodeficiency, one X-linked agammaglobulinaemia, one X-linked immunoglobulin deficiency of uncertain cause and three isolated IgG subclass deficiency. We have confirmed that lymphoma in antibody deficiency is predominantly B cell in origin. Clonal lymphocyte populations were demonstrated in biopsies irrespective of histology (16/19 with lymphoma and 11/15 without). Isolated evidence of clonality in biopsy material is therefore an insufficient diagnostic criterion to determine malignancy. Furthermore, our data suggest that clonal expansions are rarely the result of Epstein-Barr virus-driven disease.

Misdiagnosis of hereditary angio-oedema type 1 and type 2.

BACKGROUND: Hereditary angio-oedema is a rare, life-threatening, autosomal dominant condition caused by deficiency (type 1) or dysfunction (type 2) of complement C1 inhibitor. Serological assays to measure C1 inhibitor concentration and function are widely available. However, expert interpretation may not be. OBJECTIVE: To review all cases within three NHS Trusts with a putative diagnosis of hereditary angio-oedema. METHOD: Review of laboratory results and clinical notes of 44 cases of presumed hereditary angio-oedema. RESULTS: Audit revealed that 11 of 42 (26%) cases had been incorrectly considered to have a diagnosis of hereditary angio-oedema. Two of 44 had insufficient data to assess. All 11 had low functional C1 inhibitor recorded at presentation. RESULTS: available in these 11 cases at the time of diagnosis showed a normal or borderline C4 level (>or= 50% of mean normal, in contrast to hereditary angio-oedema, where C4 was less than 40% of mean normal) indicating that the low C1 inhibitor levels were a result of sample decay. Cases incorrectly diagnosed were predominantly female and had a mean age at presentation of 40 years (compared with 22 years for type 1 hereditary angio-oedema). Six of the 11 cases were offered C1 inhibitor concentrate (pooled plasma product) as treatment. CONCLUSION: We recommend that all suspected cases of hereditary angio-oedema are reviewed, that specialist advice is sought before making the diagnosis and that the diagnosis is only made after initial abnormal serology is confirmed on a second sample.

Scedosporium apiospermum in chronic granulomatous disease treated with an HLA matched bone marrow transplant.

A patient with chronic granulomatous disease who was being treated with steroids was diagnosed with a soft tissue Scedosporium apiospermum infection. Despite extensive treatment with antifungals progression to involve solid tissue (bone) occurred. Treatment required an HLA matched bone marrow transplant, which led to complete clearance of the fungal infection, although the patient subsequently died.

Proposed use of adrenaline (epinephrine) in anaphylaxis and related conditions: a study of senior house officers starting accident and emergency posts.

Senior house officers (SHOs) (n=78) at the start of their accident and emergency (A&E) post were given an anonymous five case history questionnaire, containing one case of true anaphylaxis, and asked to complete the medication they would prescribe. In the case of anaphylaxis, 100% would administer adrenaline (epinephrine) but 55% would do so by the incorrect route. In the remaining cases, 10%-56% would be prepared to administer adrenaline inappropriately. Only 5% were able to indicate the correct route and dose of adrenaline according to Resuscitation Council guidelines (UK). This has implications for training as the survey took place before the start of the A&E posting. Anaphylaxis is over-diagnosed and poorly treated despite Resuscitation Council guidelines.

Takayasu arteritis: a review.

Takayasu arteritis is a well known yet rare form of large vessel vasculitis. This review details the history, clinical features, differential diagnoses, classification, and immunology of the disorder. Suppression of inflammation and preservation of vascular competence are the aims of treatment. As with any rare disease, randomised controlled treatment trials are either lacking or based on small patient numbers, making management decisions difficult. Current evidence based treatments are presented and discussed.

A multicentre evaluation of the diagnostic efficiency of serological investigations for C1 inhibitor deficiency.

AIM: To determine the diagnostic efficiency of assays routinely used in the investigation of hereditary angio-oedema. METHODS: Over a four year period, 1144 samples were received for analysis from 907 patients suspected of C1 inhibitor deficiency. Analyses were performed for C4 and C1 inhibitor (functional and immunochemical). Notes were reviewed retrospectively on patients with low serological indicators to determine diagnosis. RESULTS: These are the first data to indicate the sensitivity, specificity, and predictive values of the assays most frequently used to screen for C1 inhibitor deficiency. A combination of low C4 and low C1 inhibitor function has 98% specificity for C1 inhibitor deficiency in this population and a 96% negative predictive value, and is thus a very effective screen. All patients with untreated C1 inhibitor deficiency had a low C4 value. CONCLUSIONS: All patients considered for a diagnosis of C1 inhibitor deficiency should have serum examined to measure both C4 and functional C1 inhibitor. If either is normal at presentation this essentially excludes a diagnosis of C1 inhibitor deficiency. These tests can be performed sequentially. If C4 is normal it is not necessary to proceed to C1 inhibitor analysis. If C1 inhibitor function and C4 are both low then a repeat sample should be obtained to confirm the findings.

Treatment of EBV driven lymphoproliferation with erythrophagocytosis: 12 year follow up.

This is a report of a case of Epstein-Barr virus (EBV) associated haemophagocytic syndrome in a 17 year old woman with antibody deficiency. For two years before this presentation, serology showed abnormally high titres to EBV early antigen, suggestive of persistent infection with EBV. She became acutely unwell with clinical features consistent with virus associated haemophagocytic syndrome (VAHS). Histology showed lymphoproliferation with erythrophagocytosis and evidence of EBV encoded RNAs in liver, spleen, and lymph node. VAHS is often fatal, particularly when it occurs in patients with underlying immunodeficiencies. In this case, treatment with intravenous immunoglobulin, aciclovir, and alpha interferon was followed by a dramatic recovery. Twelve years later the patient remains relatively well on regular intravenous immunoglobulin.

Desensitization to co-trimoxazole (trimethoprim-sulphamethoxazole) in HIV-infected patients: is patch testing a useful predictor of reaction?

OBJECTIVE: To establish the safety and efficacy of desensitization to co-trimoxazole in hypersensitive HIV-infected subjects. To assess if delayed hypersensitivity (type IV) to co-trimoxazole predicts those unable to be desensitized. METHOD: desensitization to co-trimoxazole, comprising trimethoprim (T) 0.4 mg and sulphamethoxazole (S) 2 mg initially with doubling dose daily, full strength co-trimoxazole (T/S 160 mg/800 mg) at 10 days. Patch testing with 4.5% and 9% co-trimoxazole in yellow soft paraffin, CMI Multitest. RESULTS: nineteen patients, 18 male and one female, were recruited and completed the desensitization regime. Of these 80%(15) achieved successful desensitization. Three of those who reacted did so within 18 days. All patients were successfully managed in an outpatient setting. There were no major adverse reactions. Of those reacting none gave a positive patch test to co-trimoxazole and all showed absent delayed type hypersensitivity reactions to recall antigens. CONCLUSIONS: co-trimoxazole desensitization is a safe and efficacious procedure, with a success rate of 80% using the above regime. Patch testing with co-trimoxazole gives no useful information about those that reacted.

Correlation between total and CD4 lymphocyte counts in HIV infection: not making the good an enemy of the not so perfect.

The aim of this study was to assess the correlation and average cost of total lymphocyte count compared with CD4 count as a broad estimate of immunosuppression in HIV-1 infected individuals. Spearman's partial rank correlation were calculated between total lymphocyte count, absolute CD4 count and CD4 per cent stratified by stage of HIV-1 infection for routinely collected samples. Data were collected prospectively from a T cell-subset register combined with clinical data obtained retrospectively from case notes of HIV-infected patients managed at St Mary's Hospital, London 1982-1991. Costing data were obtained through a survey of the departments of haematology and immunology (1989/90 prices). The correlation between 1534 paired absolute lymphocyte count and CD4 lymphocyte count was found to be high (R = 0.76). When analysed by stage of HIV infection, the correlation increased from R = 0.64 for asymptomatic patients, to R = 0.72 for patients with symptomatic non-AIDS HIV infection and R = 0.73 for AIDS patients. Correlations between absolute lymphocyte count and CD4 per cent were considerably weaker: R = 0.41 all paired counts; R = 0.32 for asymptomatic patients; R = 0.25 for symptomatic non-AIDS patients; R = 0.32 for AIDS patients. Average cost was pounds 8 per full blood count compared with pounds 38 per T-cell subset analysis. The high correlation between total and CD4 lymphocyte counts, especially for patients with symptomatic HIV disease, demonstrates the suitability of the use of total lymphocyte count in the absence of CD4 counts. Given the considerably lower prices of total lymphocyte counts compared with T-cell subset analysis, this is particularly relevant for developing countries.